This invention relates to an improved system for storing items while they are being sterilized, while they are being stored awaiting use, while they are in the process of being used, and after they have been used and are awaiting resterilization. The system is particularly useful in connection with the sterilization and storage of medical items, such as surgical instruments.
The most commonly used method for sterilizing surgical instruments and other medical items is to place them in towels which are enclosed in a sheet and taped shut for placing in a sterilizing autoclave. Sterilizing steam applied to the interior of the autoclave penetrates the porous materials surrounding the items to be sterilized. Moisture is removed by a vacuum drying cycle within a vacuum autoclave. When pressure is then returned to normal by admitting room air, unsterile air and lint from the towels are drawn into the center of the package. When the package is removed from the autoclave and cooled, additional room air circulates into the package. Thus, the items are immediately contaminated to some extent. If the package is not used immediately and placed in storage for a period of time, it must be returned to the autoclave for resterilization. It is estimated that two-thirds of sterilization work load in many hospitals is for items that were not used within the shelf life of the pack. This of course is an expensive and inefficient procedure which adds to the skyrocketing costs of medical treatment. Thus, a need exists for a practical and reliable system for handling sterile items and for maintaining sterility.
The above-referenced patent applications and two earlier patent applications, Ser. No. 710,521, filed Aug. 2, 1976, which was abandoned in favor of application Ser. No. 882,489, filed Mar. 1, 1978, now issued as U.S. Pat. No. 4,228,914 on Aug. 21, 1980, and Ser. No. 710,522, filed Aug. 2, 1976 now U.S. Pat. No. 105,407 in the name of Roger S. Sanderson disclose containers in which the items to be sterilized are placed within the container and the container is then placed within an autoclave or other sterilizer. The container is initially sufficiently open to permit the sterilizing environment to circulate within the interior of the container and the container is then sealed at an appropriate stage to maintain sterility. Further, the container in the earlier joint inventor cases is constructed such that steam can escape or be withdrawn from the container when the pressure on the interior of the container exceeds the pressure on the exterior. Consequently, the container is usually essentially dry with a vacuum type autoclave wherein a vacuum is applied to the container at the end of the steaming cycle. Also, only a slight amount of moisture remains in the container with a gravity-type autoclave for most sterilizing operations, and this moisture can be absorbed by a small quantity of dessicant.
However, in U.S. application, Ser. No. 821,042, referred to above, it is explained that with loads involving a considerable mass, such as a large quantity of surgical instruments, steam must be circulated through the autoclave for a considerable period of time to heat the load to the necessary sterilizing temperature. During this operation a considerable amount of steam condenses on the colder metal. Although this condensate is eventually sterilized in the autoclave, it is desirable that the container in which the load is stored be as dry as possible. In that application a container is provided and claimed having a valve in its lower wall which remains open until the pressure drops at the end of a steaming phase of a sterilizing cycle. Consequently, any condensate occurring drains from the container through the open valve.
The valve closing means includes an inflatable chamber which is initially open to high pressure steam in an autoclave, and is then automatically closed in response to the steam temperature, capturing a quantity of high pressure steam within the expandable chamber. This steam causes the chamber to expand at the end of the steaming phase of the cycle when there is a significant pressure drop. The force created by the expanding chamber is employed to close the valve in the container wall.
The container lid, gasket and base are constructed such that residual steam can be withdrawn from the container even after the valve is closed when the pressure on the exterior of the container is less than the pressure on the interior of the container. Moreover, when the pressure on the exterior is increased, this pressure holds the valve in closed position and draws the lid more tightly on the base.